Refrigerating apparatus



July I,- 1930.

s. CLAIBORNE REFRIGERATING APPARATUS Filed April 50, 1927 wig fit f: U l.

Patented July 1, 1930 UNlTED STATES PATENT OFFICE SIDNEY CLAIBORNE, 013' FORT WORTH, TEXAS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO FRIGIDAIRE CORPORATION, A CORPORATION OF DELAWARE REFRIGERATIN'G- APPARATUS Application filed April 30,

This invention relates to mechanical refrigeration and particularly to a mechanically refrigerated cooling unit for cooling various types of commercial refrigerator cabinets such as show-case refrigerators.-

One object of the invention is to improve the efficiency of the transfer of heat from the air circulating within the cabinet to the refrigerant by preventing the frosting of the metal walls of the cooling unit while atthe same time effecting satisfactory refrigeration. p

More particularly it is anobject of this invention to provide certain improvements in refrigerating apparatus described and claimed in the copending application of Philip M. Bratten, Serial No. 187,929 filed April 30, 1927. One feature of-the Bratten apparatus isthe use of relatively large air flues surrounded by relatively narrow brine ducts soTffat, heat may be transferred from thecirculating air to therefrigerant more rapidly than heretofore. By using relatively large metal surfaces in contact with the circulating air the average temperature of the brine may be higher than in the conventional brine tank; consequently there will be less accumulation of frost upon these surfaces during the active periods of the operation of the refrigerating machine, and the metal surfaces will be refrosted during the idle periods. By providing relatively narrow brine passages between the metal heat transfersurfaces, substantially all of the brine is caused tocirculate actively so that heat will be conducted from the metal walls to the refrigerant eva orator more rapidly than heretofore, with t 1e result that the duration of the active period of the ma chine is reduced.

, It is therefore apparent that refrigeration can be obtained more economically than heretofore, because the heat transferring media, the metal walls and the brine, are caused to operate more efiiciently, and because the machine is not required to reduce the pressure upon the refrigerant to the low point necessary heretofore, since the average brine temperatureis highen.

One ob ect of the present invention is'to 1927. Serial No. 187,927.

minimize the accumulation of frost upon the metal heat-transfer surfaces of the cooling unit during the active period of operation of the refrigerating machine while maintaining the cooling unit in relatively small and compact form. This object is accomplished by providing the brine duct walls with heat absorbing plates or fins projecting into the air flues of the cooling unit. Bfy using such fins, the average temperature 0- the brine may be even higher than in the Bratten apparatus; consequently there will be substantiallyv no accumulation of frost upon the metal heat-transfer surfaces to hinder the transfer; of heat thereto even during the active period of machine operation. Although the heat transfer walls and the fins are maintained at a tem erature higher than the freezing point of t e moisture which condenses thereon, the temperature of the circulating air will'be sufiicient- 1y low for satisfactory refrigeration by reason of the presence of "the relatively large metallic heat-transfer surfaces maintained free of frost at all times.

Further objects and advantages of the resent invention will be apparent from the ollowing description, reference being had to the accompanying drawings, .wherein a preferred form of embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a vertical view of a show-case refrigerator cabinet equipped with a cooling unit embodying the present invention Fig. 2 is a top view partly broken away, of the cooling unit; and

Fig. 3 is a sectional view on the line 3-3 of Fig. 2.

In Fig. 1, 20 designates a cabinet having solid insulating walls 21, 22 and 23 and other insulating walls provided by dead air spaces between a plurality of plates of glass ,24 and 25. A partition 26 divides the interior of the cabinet into a cooling compartment 28 and a food or other display compartment 27 The cooling unit 30 includes a shell brine tank comprising a sheet metal container made of tin-plated copper or galvanized iron longitudinal sectional the outside wall of the chamber 31 and is secured by a flan ed collar 43 and a clamping disc 4A forming one end of the boiler. Pipes 46 and 47 conduct refrigerant resyi eiftively into and out of the boiler 40. e chamber and ducts should be filled with brine or'other low freezing-point li uid up to about one inch below the top of t e container and the boiler should not be located too low in the chamber 31, otherwise only the brine at the lower levels will effectively circulate and be cooled. Preferably the top of the boiler should be about one inch below the level of the brine. It has been found that with a cooling coil located low in a dee tank, the brine above the coil does not coo down to the temperature desired, since it remains above the freezing point even when the rest of the brine may be at or below freezing temperature.

The unit 30 is supported above the bottom of the cooling chamber 28 and is spaced from the chamber walls and bafie 26 so that air may circulate freely around the unit as well as through its fines. The combinedsurface of the exposed vertical walls of the unit should at least be equal to the exposed surface of the block of ice which would be required to cool the cabinet. By providing relatively narrow brine ducts and relatively large flue openings, a relatively ter exposed area may easily be provide by a cool. ing unit which will occupy a smaller s ace than the ice block. The space require by the unit need be no more than approximately two-thirds of the cubical content of the cool,- ing chamber 28, and may be slightly less if necessary to provide at least three inches of space between the walls of the unit and the cooling chamber walls so that air may circulate freely about and through the unit. The matter of clearance is important, because frosting of the tank and ducts tends to decrease the clearance and might even close it off entirely, preventing free circulation of the air. Unless the air can circulate freely adjacent the walls of the cooling unit it can not absorb the heat from the air. or the same reason the flue openings should be at least four inches in width. If the tank and ducts are made of sheet metal sufliciently thin to permit making the joints by lockseaming and soldering, the width of the ducts need be only one inch. If heavier sheet material is required on account of the size of treated the cooling unit, and'the joints must therefore be riveted, the ducts may be two inches wide to allow for introducing riveting tools between the metal sheets forming the ducts. There is no object in making the ducts wider than one inch except to facilitatemanufacture. Generally, the brine ducts should be from about one to two inches wide and the flues preferably at least four times as wide as the ducts, although if desired, for some purposes the ducts may be of even less'width.

The circulation of air within the cabinet is indicated roughly by the arrows 50, 51. 52 and 53. Shelves or other baflies (not shown) may be provided in the food chamber 27 for securing a fairly even distribution of the air circulating therein.

If more than one unit is used in' a cooling chamber, at least four inches and preferably six inches should be left between the tank for circulation and to prevent the space from being stopped up with frost.

One of the features of the Bratten apparatus is the use of such' a relatively large metal, heat-absorbing surface adjacent which the air may circulate freely, that it is possible to effect satisfactory refrigeration by brine or other heat transfer medium working at temperatures higher than permissible in brine tanks used heretofore. 'Al- 5 though, during the active period of operation of the refrigerating machine frost may collect upon-the metal surfaces, these surfaces will be defrosted during the idle periods of the machine. Another feature is the circulation of brine through relatively narrow ducts between the metal heat-absorbing surfaces. Substantially all of the brine which is cooled by the evaporator is caused to circulate actively so that heat will be conducted from the metal walls to the evaporator more rapidly than heretofore, with the result that the duration of the active period of the refrigerating machine is reduced.

The present invention solves the problem of preventing the accumulation of frost upon the metal surfaces surrounding the air flues during the operation of the refrigerating machine. The walls surrounding the fines 37 and 38 are provided with metal, heat-absorbing plates or fins 60 and 61 which present a greater total area of metal heat transfer surface to the air circulating through the fines than in the cooling unit disclosed in the Bratten application referred to. These fins are attached in ood'thermal contact to the walls of .the ues and the opposing rows of fins are preferably disposed in staggered or offset relation with respect toeach other as shown in Fig. 2 in order to secure a better flue effect and to prevent frost from bridging across the fins and thereby impeding the circulation of air. Consequently the temperature of the brine may be maintained above the freezing point brine may be higher than heretofore. Therefore the refrigerating machine may be operated more economically since it is not necessary toreduce the pressure upon the refrigerant in the evaporator to that low point required by apparatus in which the working temperature of the brineis lower.

The ,coolingunit may be provided with horizontal or'vertical flues accordin to the type of refrigerator cabinet with .wh1ch they are intended to be used. Vertical flues are preferable, owing to the natural tendency of air to descend on being chilled." However, the invention is not limited to cooling unitsor tanks with vertical flues, as a cooling unit with horizontal flues may be used advantageously in some ty es of cabinets for example, a showcase ca inet not provided with a baflle, to separate the food com partment from the coolin compartment.

Where the term brine is used in the specification and claims, it refers to any low freezing point li uid or solution which is suitable for trans erring heat from the heat transfer walls of the cooling unit to the evaporator. i

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to-be'understood that other forms might be ado ted, all comin within the scope of the -c aims which fol ow.

What is claimed is as follows:

1..-Refrigerating ap aratus comprisin a shell tank having t ermally conducting walls of relatively great area, air flues bounded by said walls, a refri erating medium in said tank, ducts adapted to circulatev a relatively small amount of refri eratin medium in contact with said wa ls, an thermall conductin fins extending from said wa'l s into said ues in contact with air circulating adjacent said ducts, the total area of the walls and fins being adaptedto reduce the circulating air to the desired temperature and .to mamtain the temperature of the fins above the freezing point of the moisture condensed thereon.

2. Refrigerating ap aratus comprising a shell tank having t ermally conducting walls of relatively great area, air flues bounded and formed by said walls, a refrigerating medium in said tank, a chamber within said tank adapted to contain refrigerating medium and a refrigerating unit, ducts adapted to circulate a relatively small amount of said refrigerating medlum in contact with said .walls and thermally conducting fins extending from said walls into said flues in'contact with air circulating adj acent said ducts, the total area of said walls and fins being adapted to reduce the circulating air to the desired temperature and to maintain the temperature of the fins above the freezing point of the moisture condensed thereon. Y I 3. In a device of the character described a relatively narrow brine duct shaped to' a relatively narrow brine'duct shaped to.

form an air flue of relatively large opening,

rows of fins extending within'said flue, sa1d fins being attached to the duct walls enclosing and forming said flue, the fins of one row being disposed in off-set relation with respect to the fins of the opposing row.

5. Aplparatus according to claim- 1 including a re atively narrow brine duct enclosing and forming a flue of relatively large open-. ing, fins extending within the flue and attached to the duct walls enclosing said flue, the flue being greater in width than the width of the brine duct.

6. Apparatus according to claim 1 including a relatively narrow brine duct enclosing and forming a flue of relativel large opening, fins extending within the-- ue' and attached to the duct walls enclosing said flue, said brine duct being substantially from one to two inches wide and the flue at least four times the width of said brine duct.

7. A shell brine tank com osed of substantially parallel walls space to form brinecarryin'g ducts, a brine chamber in said tank, brine "cooling means in said chamber, air flues formed in said tank by said brine-car.- rying' ducts and'fins on the walls. of said ducts extending into said flues.

8. A shell brine tank composed of substantially parallel walls spaced to ,form brine-carrying ducts, a brine chamber in said tank brine cooling means in said chamber air flues formed in said tank by said brinecarrying ducts and fins in the walls of said ducts extendin into said flues, said ducts 'being apprecia 1y smaller in width than ion us i

.ing ue, an sorbing member in thermal contact with a absorb member in thermal contact with a wall 0 said tank and extending into said 10. In a refrigerating device, a shell tank comprising a plurality of vertically extending hollow walls to form a chamber-adapted to contain refrigerating medium, said walls bein arranged to form a vertically extenda vertically extending heat abgall of said tank and extending into said In testimony whereof hereto afiix my signature. v

SIDNEY CLAIBORNE.

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